SAL 1950 Box Car Rebuilding Program

I'm looking for information on Seaboard's 1951 box car rebuilding program. SAL rebuilt most B-4 and B-5 composite box cars with steel siding and other new appliances. At least some of the cars (and many of the B-3s) were modified for maintenance service. Do you know when the program started and where the cars were rebuilt? I'm also looking for how many cars were rebuilt and what slogans were applied (if any). Thanks for whatever information you can provide. Please reply here or off-list at Golden1014@yahoo.com. Thanks!